Dual liquid crystal display device

ABSTRACT

A dual liquid crystal display device includes a transmissive liquid crystal display panel; a reflective liquid crystal display panel formed on the same substrate as the transmissive liquid crystal display panel; a first light guide block disposed under the transmissive liquid crystal display panel and having dot patterns formed on a first surface thereof; a second light guide block disposed under the reflective liquid crystal display panel and having V-grooves formed on a first surface thereof; a light source disposed adjacent to the first light guide block; a housing in which the transmissive and reflective liquid crystal display panels, the light source and the light guide blocks are seated, the housing having an opening to correspond to an image display surface of the reflective liquid crystal display panel; a dual brightness enhancement film provided in a region corresponding to the opening of the housing.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, andclaims all benefits accruing under 35 U.S.C. §119 from an applicationfor DUAL LIQUID CRYSTAL DISPLAY DEVICE earlier filed in the KoreanIntellectual Property Office on 24 Jun. 2008 and there duly assignedSerial No. 10-2008-0059657.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a dual liquid crystal display device comprising afirst transmissive liquid crystal display panel and a second reflectiveliquid crystal display panel.

2. Description of the Related Art

A liquid crystal display device is a flat panel display havingadvantages that it is manufactured in a small and thin scale and drivenwith low power consumption, and therefore it has been used in portablecomputers such as notebook PCs, office automation equipments,audio/video equipments, etc. Examples of such devices are as follows:

U.S. Pat. No. 7,193,666 to Jung-Min Choi et al. and entitled DUAL LIQUIDCRYSTAL DISPLAY DEVICE describes an LCD device for performingbi-directional display. The LCD device includes first and second displayunits, and a light supplying unit. The first display unit includes anLCD panel and a transflective film that is disposed under the LCD paneland has layers in which first and second layers having differentrefractivity indexes are alternately stacked. The transflective filmpartially reflects and transmits light incident onto the film. The lightsupplying unit is disposed between the first and second display units,and provide the first and second display units with light generated froma lamp by dividing the light, to thereby regulate a contrast ratio of aluminance between the first and second display units;

U.S. Pat. No. 7,075,597 to Chi-Jain Wen et al, and entitled DUAL-SCREENLIQUID CRYSTAL DISPLAY discloses a dual-screen liquid crystal displayincluding three substrates. The first substrate has a first surface anda second surface. The first reflector layer, the first liquid crystallayer, the second substrate and the first polarization film aresequentially disposed on the first surface of the first substrate toform the first reflective LCD. The second reflector layer, the secondliquid crystal layer, the third substrate and the second polarizationfilm are sequentially disposed on the second surface of the firstsubstrate to form the second reflective LCD; and

U.S. Pat. No. 7,034,799 to Seog-Geun Lee et al. and entitledBACKLIGHTING DEVICE FOR DUAL LIQUID CRYSTAL DISPLAY AND FOLDER-TYPEMOBILE PHONE THEREWITH describes a backlighting device for a dual LCD(Liquid Crystal Display). The backlighting device includes a circuitboard with a through hole; a backlighting illumination device situatedwithin the hole for radiating light in a first direction substantiallyperpendicular to a first face of the circuit board and in a seconddirection substantially perpendicular to a second face of the circuitboard; a main LCD being situated on one face of the backlightingillumination device in the first direction, for displaying firstinformation in the first direction; and a slave LCD being situated onanother face of the backlighting illumination device through the throughhole in the second direction, for displaying second information in thesecond direction.

A liquid crystal display device functions to display a picture or animage by controlling an electric field to transmit or cut off light, theelectric field being applied to liquid crystal materials havingdielectric anisotropy. The liquid crystal display device uses anexternal light without generating light by itself, unlike displaydevices, such as an organic light emitting display device (OLED) and acathode ray tube (CRT), that generate light by itself.

In general, the liquid crystal display devices are mainly divided intotransmissive and reflective liquid crystal display devices, depending onthe manners of employing light.

That is to say, the liquid crystal display devices are divided into atransmissive liquid crystal display device and a reflective liquidcrystal display device, depending on whether it uses a separatebacklight unit or reflected external light as its power source, andthere has also been an attempt to develop a transflective liquid crystaldisplay device in which a transmissive liquid crystal display device arecombined with a reflective liquid crystal display device.

Also, a dual liquid crystal display device displaying a picture on bothsides of a liquid crystal display device has been developed recently.The dual liquid crystal display device display a picture on both sidesthereof since it includes a main liquid crystal display panel and a subliquid crystal display panel, both of which are formed on both sidesthereof, respectively.

However, conventional dual liquid crystal display devices havedisadvantages that they are thick and heavy, and their power consumptionis high since a backlight unit needs to be installed for each of themain liquid crystal display panels and the sub liquid crystal displaypanels.

This trend runs against small and thin portable devices such as mobilephones using a liquid crystal display device, and therefore the liquidcrystal display device has major problems in aspect of slimness and costefficiency.

SUMMARY OF THE INVENTION

Accordingly, the present invention is designed to solve such drawbacksof the prior art, and therefore an object of the present invention is toprovide a dual liquid crystal display device including a firsttransmissive liquid crystal display panel to display an image on a firstsurface and a second reflective liquid crystal display panel to displayan image on a second surface and being able to maximize slimness andcost efficiency by forming the first and second liquid crystal displaypanels with the same substrate.

Also, another object of the present invention is to provide a dualliquid crystal display device having a light guide formed in lowerportions of the first and second liquid crystal display panels, thelight guide including a first light guide block corresponding to thefirst liquid crystal display panel and having dot patterns formed in apredetermined surface thereof, and a second light guide blockcorresponding to the second liquid crystal display panel and havingV-grooves formed in a predetermined surface thereof, and particularlybeing able to control brightness uniformity, achieve enhanced contrastratio at night and improve the brightness by forming a dual brightnessenhancement film on a corresponding surface of the second light guideblock.

One embodiment of the present invention is achieved by providing a dualliquid crystal display device including a first liquid crystal displaypanel displaying an image on a first surface thereof; a second liquidcrystal display panel formed on the same substrate as the first liquidcrystal display panel to display an image on a second surface thereof; alight source disposed at an adjacent side under the first liquid crystaldisplay panel; a light guide disposed under the first and second liquidcrystal display panels and including a first light guide blockcorresponding to the first liquid crystal display panel and having dotpatterns formed in a first surface thereof and a second light guideblock corresponding to the second liquid crystal display panel andhaving V-grooves formed on a first surface thereof; a housing settlingthe first and second liquid crystal display panels, the light source andthe light guide and having an opening to correspond to an image displaysurface of the second liquid crystal display panel; a dual brightnessenhancement film provided in a region corresponding to the opening ofthe housing.

In this case, the first liquid crystal display panel may be realizedwith a transmissive liquid crystal display panel, and the second liquidcrystal display panel may be realized with a reflective liquid crystaldisplay panel.

Also, the first and second liquid crystal display panels may be formedrespectively in different regions (a first region and a second region)of first and second substrates that are a pair of the same substrates.

Additionally, a thin film transistor array and a transparent electrodemay be formed in a region corresponding to the first region of the firstsubstrate, a thin film transistor array and a reflective electrode maybe formed in a region corresponding to the second region of the firstsubstrate, and a common electrode and a color filter pattern may beformed in the first and second regions of the second substratecorresponding to the first and second regions of the first substrate,respectively.

In addition, a drive circuit block driving the first and second liquidcrystal display panels may be installed at one side of the firstsubstrate outside the first or second region, and first polarizingplates and second polarizing plates may be formed on upper/lower sidesof the first and second liquid crystal display panels, respectively.

Also a polarizing plate may be further formed on a predetermined surfaceof the dual brightness enhancement film.

Furthermore, the first light guide block may be disposed adjacent to thelight source.

According to the present invention as described above, the dual liquidcrystal display device is advantageously manufactured to be slim inthickness since it has a dual structure with the same thickness as theconventional single structure liquid crystal display devices. Also, thedual liquid crystal display device according to the present inventionhas advantages in aspect of cost efficiency in that the manufacturingcost such as the material cost and the processing cost may besignificantly reduced by realizing a liquid crystal display device witha dual structure using one sheet of panel.

Also, a light guide is formed under the first and second liquid crystaldisplay panel, the light guide including a first light guide blockcorresponding to the first liquid crystal display panel and having dotpatterns formed on a predetermined surface thereof, and a second lightguide block corresponding to the second liquid crystal display panel andhaving V-grooves formed on a predetermined surface thereof, andparticularly being able to control brightness uniformity, achieveenhanced contrast ratio at night and improve the brightness by forming adual brightness enhancement film on a corresponding surface of thesecond light guide block.

Also, the dual liquid crystal display device according to the presentinvention has advantages that its brightness uniformity may becontrolled in a more effective manner since the first liquid crystaldisplay panel as the transmissive liquid crystal display panel isdisposed adjacent to a light source.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or similar components, wherein:

FIG. 1 schematically illustrates a configuration of a dual liquidcrystal display device according to one exemplary embodiment of thepresent invention;

FIG. 2 schematically illustrates an operation of the dual liquid crystaldisplay device as shown in FIG. 1;

FIG. 3 is a cross-sectional view showing a region corresponding to afirst liquid crystal display panel in the dual liquid crystal displaydevice as shown in FIG. 1;

FIG. 4 is a cross-sectional view specifically showing a first substrateas shown in FIG. 3;

FIG. 5 is a cross-sectional view showing a region corresponding to asecond liquid crystal display panel in the dual liquid crystal displaydevice as shown in FIG. 1 and

FIG. 6 is a cross-sectional view specifically showing a first substrateas shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, only certain exemplaryembodiments of the present invention have been shown and described,simply by way of illustration. As those skilled in the art wouldrealize, the described embodiments may be modified in various differentways, all without departing from the spirit or scope of the presentinvention. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. In addition, when anelement is referred to as being “on” another element, it can be directlyon the element or be indirectly on the element with one or moreintervening elements interposed therebetween. Also, when an element isreferred to as being “connected to” another element, it can be directlyconnected to the element or be indirectly connected to the element withone or more intervening elements interposed therebetween. Hereinafter,like reference numerals refer to like elements.

FIG. 1 schematically illustrates a configuration of a dual liquidcrystal display device according to one exemplary embodiment of thepresent invention, and FIG. 2 schematically illustrates an operation ofthe dual liquid crystal display device as shown in FIG. 1.

Referring to FIG. 1, the dual liquid crystal display device 1 accordingto one exemplary embodiment of the present invention includes a firstliquid crystal display panel 10 displaying an image on a predeterminedsurface thereof; a second liquid crystal display panel 20 formed on thesame substrate as the first liquid crystal display panel 10 to displayan image on a predetermined surface thereof, a light guide disposedunder the first and second liquid crystal display panels, the lightguide 34 including a first light guide block 34′ corresponding to thefirst liquid crystal display panel 20 and having light reflecting dotpatterns 31 formed on a predetermined surface thereof, and a secondlight guide block 34″ corresponding to the second liquid crystal displaypanel 20 and having V-grooves 33 for reflecting light formed on apredetermined surface thereof; a light source 32 disposed adjacent thefirst guide block 34′, the light source 32 emitting light into the firstlight guide block 34′; and a housing 40 housing the first and secondliquid crystal display panels 10 and 20, the light source 32, the firstlight guide block 34′ and the second light guide block 34″, the housinghaving opening 42 correspond to the second surface, i.e., image displaysurface, of the second liquid crystal display panel 20.

In this case, it is characterized in that the first liquid crystaldisplay panel 10 is provided as a transmissive liquid crystal displaypanel, and the second liquid crystal display panel 20 is provided as areflective liquid crystal display panel.

Also, the transmissive and reflective liquid crystal display panels 10and 20 are formed using a pair of the same substrates. For this purpose,a thin film transistor array (not shown) and a transparent electrode(not shown) are formed in a region corresponding to a first region ofthe first substrate 100, and a thin film transistor array (not shown)and a reflective electrode (not shown) are formed in a regioncorresponding to a second region of the first substrate 100. Also, acommon electrode (not shown) and a color filter pattern (not shown) areformed in a first region and a second region of the second substrate 200corresponding respectively to the first and second regions of the firstsubstrate 100. A liquid crystal layer (not shown) is formed between thefirst substrate 100 and the second substrate 200. Also, first polarizingplates 120 and second polarizing plates 220 are formed on upper andlower sides of both the transmissive and reflective liquid crystaldisplay panels 10 and 20.

The transmissive liquid crystal display panel 10 is formed in the firstregions of the first substrate 100 and the second substrate 200 via thefirst polarizing plates 120 and the second polarizing plates 220, andthe reflective liquid crystal display panel 20 is formed on the secondregions of the first substrate 100 and the second substrate 200.

Also, a drive circuit block 130 to drive the transmissive and reflectiveliquid crystal display panels 10 and 20 is installed on one side of thefirst substrate 100 disposed outside the region of the transmissiveliquid crystal display panel 10.

The backlight unit 30 includes the light source 32 and the light guide34, as shown in FIG. 1. In particular, the light guide 34 is disposed inthe first region and the second region, that is, in the regionscorresponding to the transmissive and reflective liquid crystal displaypanels 10 and 20. The light guide 34 includes a light guide block 34′corresponding to the transmissive liquid crystal display panel 10 andhaving dot patterns 31 formed in a predetermined surface thereof, and alight guide block 34″ corresponding to the reflective liquid crystaldisplay panel 20 and having V-grooves 33 formed on a predeterminedsurface thereof. The light guide block 34′ and the light guide block 34″are used to facilitate the control of the brightness uniformity for thetransmissive liquid crystal display panel 10, and also to facilitate thecontrol of the quantity of light and other characteristics for thereflective liquid crystal display panel 20.

Also, the exemplary embodiment of the present invention is characterizedin that a dual brightness enhancement film (hereinafter, referred to as‘DBEF’) 50 is provided in a region corresponding to an image displayingsurface of the reflective liquid crystal display panel 20 and adjacentthe second light guide block 34.″

The DBEF 50 has a stacked structure in which several tens of films arealternately stacked, wherein the films have the same refractive index inrespect to a first axis (for example, an X axis) and the differentrefractive indexes in respect to a second axis (for example, a Y axis).Therefore, the first axis having the same refractive index is referredto as a transmission axis, and functions to transmit light in a linearmanner, and the second axis having the different refractive indexes isreferred to as a reflection axis, and functions to reflect light in alinear manner.

More particularly, the DBEF 50 has a multi-layered structure in whichseveral hundreds of thin films formed of two different materials arealternately stacked. That is to say, the DBEF 50 is formed byalternatively stacking poly-ethylene naphthalate layers withsubstantially high birefringence and poly-methyl methacrylate (PMMA)layers with an isotropic structure. A naphthalene group has a flat planestructure. Therefore, when one naphthalene group is disposed adjacent toanother naphthalene group, they are easily stacked, and the refractiveindex in a stacking direction is highly different from the refractiveindex in other directions. On the contrary, PMMA is an amorphous polymerhaving the same refractive index in all directions since it has anisotropic orientation. Therefore, the DBEF transmits all thepolarization components on the first axis, and reflects all thepolarization components on the second axis.

By forming the DBEF 50 on a region corresponding to the image displayingsurface of the reflective liquid crystal display panel 20, it ispossible to overcome problems caused when light transmitted through thelight guide 34 directly proceeds towards a user without entering thereflective liquid crystal display panel 20, that is, the disadvantagethat a contrast ratio of the dual liquid crystal display device issignificantly degraded since an image is unclearly projected by thereflective liquid crystal display panel 20.

Also, the contrast ratio of the reflective liquid crystal display panel20 may be further improved by forming additional polarizing plates 52 ona predetermined surface of the DBEF 50, and the improved high brightnessof the reflective liquid crystal display panel 20 may be achieved due tothe presence of characteristics of the DBEF 50 having light recyclingproperties, as shown in FIG. 1.

Referring to FIG. 2, light generated from the light source 32 enters thesecond polarizing plate 220 through the light guide block 34′ of thelight guide 34. In this case, the transmissive liquid crystal displaypanel 10 operates in a transmissive mode to display an image on anopposite surface to a surface to which light travels, that is, a displaysurface.

In this case, the present invention is characterized in that a pluralityof dot patterns 31 are formed in a predetermined surface of the lightguide block 34′. The dot patterns 31 are formed to control thebrightness for the first transmissive liquid crystal display panel 10more uniformly. That is to say, a plurality of the dot patterns 31perform a back lighting function for the transmissive liquid crystaldisplay panel 10.

Also, light, which is transmitted to the light guide block 34″, coupledto one side of the light guide block 34′, that is, the light guide block34″ disposed remotest from the light source 32, enters the secondpolarizing plate 220 of the reflective liquid crystal display panel 20,and is reflected by a reflective electrode (not shown) formed on thefirst substrate 100 of the reflective liquid crystal display panel 20.Therefore, the reflective liquid crystal display panel 20 operates in areflective mode to display an image on an image displaying surface ofthe reflective liquid crystal display panel 20.

In this case, the present invention is characterized in that a pluralityof V-grooves are formed on a predetermined surface of the second lightguide block 34. The V-grooves are formed to facilitate the control ofquantity of light and the other characteristics for the secondreflective liquid crystal display panel 20. That is to say, a pluralityof the V-grooves 33 perform a front lighting function for the reflectiveliquid crystal display panel 20.

Also, the DBEF (dual brightness enhancement film) 50 is providedadjacent the second light guide block 34.″ In this manner, it ispossible to overcome the problems caused when the light transmitted intothe light guide 34 directly proceeds towards a user (dotted arrows)without entering the reflective liquid crystal display panel 20, thatis, the disadvantages that the contrast ratio of the dual liquid crystaldisplay device is significantly degraded since an image is unclearlyprojected by the reflective liquid crystal display panel 20.

The contrast ratio of the reflective liquid crystal display panel 20 maybe further improved by forming the additional polarizing plate 52 on apredetermined surface of the DBEF 50, and the improved high brightnessof the reflective liquid crystal display panel 20 may be achieved due tothe presence of characteristics of the DBEF 50 having light recyclingproperties.

Therefore, since the light source 32 is disposed adjacent to thetransmissive region, it is easy to control the brightness uniformitythat is one of important factors in the transmissive liquid crystaldisplay device. Also, it is easy to control the light source 32 and theother characteristics since the excessive light source entering thelight guide block 34″ is used to control the reflective region.

According to one exemplary embodiment of the present invention asdescribed above, the dual liquid crystal display device is also realizedwith a pair of the same substrates. Therefore, the dual liquid crystaldisplay device are advantageously manufactured to be slim in thicknesssince it has a dual structure with the same thickness as a conventionalsingle structure liquid crystal display devices. Also, the dual liquidcrystal display device according to the present invention has advantagesin aspect of cost efficiency in that the manufacturing cost such as thematerial cost and the processing cost may be significantly reduced,compared to the conventional single structure liquid crystal displaydevices.

FIG. 3 is a cross-sectional view showing a region corresponding to afirst liquid crystal display panel 10 in the dual liquid crystal displaydevice as shown in FIG. 1. Also, FIG. 4 is a cross-sectional viewspecifically showing a first substrate as shown in FIG. 3.

Referring to FIG. 3, the light source 32 generating light and the lightguide block 34′ of the light guide supply light emitted from the lightsource 32 to the transmissive liquid crystal display panel 10 and aredisposed adjacent the transmissive liquid crystal display panel 10. Inthis case, the light source 32 and the light guide block 34′ constitutesa backlight unit 30.

In this case, the present invention is characterized in that a pluralityof dot patterns 31 are formed in a predetermined surface of the lightguide block 34′, that is, an opposite surface to a surface which lighttravels toward transmissive liquid crystal display panel 10. The dotpatterns 31 are formed to control the brightness for the firsttransmissive liquid crystal display panel 10 more uniformly. That is tosay, a plurality of the dot patterns 31 perform a back lighting functionfor the transmissive liquid crystal display panel 10.

The transmissive liquid crystal display panel 10 includes a firstsubstrate 100, a second substrate 200 disposed spaced apart from thefirst substrate 100 at a predetermined distance, and a liquid crystallayer 300 interposed between the first and second substrates. Also, thefirst polarizing plates 120 and the second polarizing plates 220 areformed on opposite sides of the transmissive liquid crystal displaypanel 10.

As shown in FIGS. 3 and 4, the first substrate 100 includes atransparent substrate 110, a thin film transistor (hereinafter, referredto as ‘TFT’) array 114 formed on the transparent substrate 110, and apixel electrode 115 formed on the TFT array 114.

The TFT array 114 is composed of a TFT 112 and a passivation layer 113to protect the TFT 112. The TFT 112 includes a gate electrode 112 a, agate insulator 112 b, an active layer 112 c, an ohmic contact layer 112d, a source electrode 112 e, and a drain electrode 112 f.

The gate electrode 112 a is provided to correspond to a light shieldinglayer 211 formed on a transparent substrate 210 of the second substrate200, and the gate insulator 112 b is formed on an overall surface of thetransparent substrate 110 on which the gate electrode 112 a is formed.The active layer 112 c and the ohmic contact layer 112 d are formed onthe gate insulator 112 b to correspond to the gate electrode 112 a. Thesource electrode 112 e and the drain electrode 112 f are disposed spaceapart from each other, and formed on the ohmic contact layer 112 d.

The source and drain electrodes 112 e and 112 f as well as the gateelectrode 112 a are also provided in a region on which the lightshielding layer 211 is formed. Therefore, the light shielding layer 211may prevent light entering the second substrate 200 from being reflectedby the gate electrode 112 a, the source electrode 112 e and the drainelectrode 112 f.

The passivation layer 113 formed on the TFT 112 partially exposes thedrain electrode 112 f of the TFT 112. The pixel electrode 115 is formedon the passivation layer 113 and the exposed drain electrode 112 f, andthen electrically coupled to the drain electrode 112 f.

The pixel electrode 115 is composed of transmissive electrodes made ofindium tin oxide (ITO), indium zinc oxide (IZO), or the like.

Also, the light shielding layer 211 and a color filter layer 212 areformed on the transparent substrate 210 of the second substrate 200, anda passivation layer 214 is formed on the light shielding layer 211 andthe color filter layer 212.

The color filter layer 212 is composed of red, green and blue colorfilters (R, G and B) that are disposed spaced apart at a predetermineddistance from each other. The light shielding layers 211 are providedbetween the color filters (R, G and B), and demarcate the regions onwhich each color filter is formed, thereby improving the colorreproducibility of each of the color filters. The passivation layer 214made of a photocurable material is formed on the color filter layer 212to protect the color filter layer 212.

A common electrode 215 is formed on the passivation layer 214. Thecommon electrode 215 is made of a transparent conductive material, andformed on the passivation layer 214 to have a uniform thickness.

The transmissive liquid crystal display panel 10 as configured thusdisplays a picture by irradiating light having entered through the lightsource 32 and the light guide 34 to the outside, that is, a displaysurface, via the liquid crystal layer 300 and the transmissive electrode115 of the transmissive liquid crystal display panel 10. That is to say,the transmissive liquid crystal display panel 10 operates in atransmissive mode.

FIG. 5 is a cross-sectional view showing a region corresponding tosecond liquid crystal display panel 20 in the dual liquid crystaldisplay device as shown in FIG. 1. Also, FIG. 6 is a cross-sectionalview specifically showing a first substrate as shown in FIG. 5.

Referring to FIG. 5, light transmitted to the light guide block 34″ ofthe light guide disposed adjacent to the reflective liquid crystaldisplay panel 20 enters the reflective liquid crystal display panel 20by means of the light guide block 34″.

In this case, it is characterized in that a plurality of V-grooves 33are formed on a predetermined surface of the light guide block 34″. TheV-grooves 33 are formed to facilitate the control the quantity of lightand other characteristics for the second reflective liquid crystaldisplay panel 20. That is to say, a plurality of the V-grooves 33perform a front lighting function for the reflective liquid crystaldisplay panel 20.

Also, the DBEF (dual brightness enhancement film) 50 is providedadjacent the second light guide block 34.″ In this manner, it ispossible to overcome problems caused when the light transmitted into thelight guide 34 directly proceeds towards a user (dotted line), withoutentering the reflective liquid crystal display panel 20. Thedisadvantage that the contrast ratio of the dual liquid crystal displaydevice is significantly degraded since an image is unclearly projectedby the reflective liquid crystal display panel 20 is thus overcome.

Also, the contrast ratio of the reflective liquid crystal display panel20 may be further improved by forming an additional polarizing plate 52on a predetermined surface of the DBEF 50, and the improved highbrightness of the reflective liquid crystal display panel 20 may beachieved due to the presence of characteristics of the DBEF 50 havinglight recycling properties.

The reflective liquid crystal display panel 20 includes a firstsubstrate 100, a second substrate 200 disposed spaced apart the firstsubstrate 100 at a predetermined distance from, and a liquid crystallayer 300 interposed between the first and second substrates.

In this case, the first substrate 100 and the second substrate 200 aredefined in the same manner as the first substrate 100 and the secondsubstrate 200 of the above-mentioned transmissive liquid crystal displaypanel 10. This is why the transmissive and reflective liquid crystaldisplay panels 10 and 20 according to one exemplary embodiment of thepresent invention are formed in different regions (first and secondregions) using a pair of the same substrates (first and secondsubstrates 100 and 200).

As shown in FIGS. 5 and 6, the first substrate 100 includes atransparent substrate 110, a thin film transistor (hereinafter, referredto as ‘TFT’) array 114 formed on the transparent substrate 110, and areflective electrode 116 formed on the TFT array 114.

The TFT array 114 is composed of a TFT 112 and a passivation layer 113to protect the TFT 112. The TFT 112 includes a gate electrode 112 a, agate insulator 112 b, an active layer 112 c, an ohmic contact layer 112d, a source electrode 112 e and a drain electrode 112 f.

The gate electrode 112 a is provided to correspond to a light shieldinglayer 211 formed on transparent substrate 210 of the second substrate200, and the gate insulator 112 b is formed on an overall surface of thetransparent substrate 110 on which the gate electrode 112 a is formed.The active layer 112 c and the ohmic contact layer 112 d are formed onthe gate insulator 112 b to correspond to the gate electrode 112 a. Thesource electrode 112 e and the drain electrode 112 f are disposed spaceapart from each other, and formed on the ohmic contact layer 112 d.

The source and drain electrodes 112 e and 112 f as well as the gateelectrode 112 a are also provided in a region on which the lightshielding layer 211 is formed. Therefore, the light shielding layer 211may prevent light entering the second substrate 200 from being reflectedby the gate electrode 112 a, the source electrode 112 e and the drainelectrode 112 f.

The passivation layer 113 formed on the TFT 112 partially exposes thedrain electrode 112 f of the TFT 112.

The reflective electrode 116 is formed on the passivation layer 113 andthe exposed drain electrode 112 f, and then electrically coupled to thedrain electrode 112 f.

The reflective electrode 116 is made of metals such asaluminum-neodymium (AlNd), and preferably patterned to have a shape of aplurality of lens so as to enhance the reflectance of the incidentlight.

Also, light shielding layer 211 and color filter layer 212 are formed onthe transparent substrate 210 of the second substrate 200, and apassivation layer 214 is formed on the light shielding layer 211 and thecolor filter layer 212.

The color filter layer 212 is composed of red, green and blue colorfilters (R, G and B) that are disposed spaced apart at a predetermineddistance from each other. The light shielding layers 211 are providedbetween the color filters (R, G and B), and demarcate the regions onwhich each color filter is formed, thereby improving the colorreproducibility of each of the color filters. The passivation layer 214made of a photocurable material is formed on the color filter layer 212to protect the color filter layer 212.

A common electrode 215 is formed on the passivation layer 214. Thecommon electrode 215 is made of a transparent conductive material, andthen formed on the passivation layer 214 to have a uniform thickness.

The reflective liquid crystal display panel 20 as thus configureddisplays a picture on the display surface thereof by allowing lighttransmitted to the light guide block 34″ to enter the reflective liquidcrystal display panel 20, pass through the liquid crystal layer 300 ofthe reflective liquid crystal display panel 20 and be reflected by thereflective electrode 116. That is to say, reflective liquid crystaldisplay panel 20 operates in a reflective mode.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, but, on the contrary, isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims, andequivalents thereof.

1. A dual liquid crystal display device, comprising: a first liquidcrystal display panel displaying an image on a display surface thereof;a second liquid crystal display panel formed on the same substrate asthe first liquid crystal display panel to display an image on a displaysurface thereof; a light guide disposed under the first and secondliquid crystal display panels, said light guide including: a first lightguide block corresponding to the first liquid crystal display panel andhaving dot patterns formed on a first surface thereof; and a secondlight guide block corresponding to the second liquid crystal displaypanel and having V-grooves formed on a first surface thereof; a lightsource disposed at an adjacent side of said first light guide block; ahousing in which the first and second liquid crystal display panels, thelight source and the light guide are seated, said housing having anopening corresponding to said display surface of the second liquidcrystal display panel; a dual brightness enhancement film provided insaid opening of said housing; and a first polarizing plate being furtherformed on a predetermined surface of the dual brightness enhancementfilm.
 2. The dual liquid crystal display device according to claim 1,wherein the first liquid crystal display panel is realized with atransmissive liquid crystal display panel, and the second liquid crystaldisplay panel is realized with a reflective liquid crystal displaypanel.
 3. The dual liquid crystal display device according to claim 1,wherein the first and second liquid crystal display panels are formedrespectively in different regions (a first region and a second region)of first and second substrates that are a pair of the same substrates.4. The dual liquid crystal display device according to claim 3, whereina thin film transistor array and a transparent electrode are formed in aregion corresponding to the first region of the first substrate, a thinfilm transistor array and a reflective electrode are formed in a regioncorresponding to the second region of the first substrate, and a commonelectrode and a color filter pattern are formed in the first and secondregions of the second substrate corresponding to the first and secondregions of the first substrate, respectively.
 5. The dual liquid crystaldisplay device according to claim 3, wherein a drive circuit blockdriving the first and second liquid crystal display panels is installedat one side of the first substrate outside the first or second region.6. The dual liquid crystal display device according to claim 1, whereinsecond polarizing plates and third polarizing plates are formed onupper/lower sides of the first and second liquid crystal display panels,respectively.
 7. The dual liquid crystal display device according toclaim 5, wherein the light source is disposed adjacent to the drivecircuit block.
 8. The dual liquid crystal display device according toclaim 1, said dual brightness enhancement film has a stacked structurein which a plurality of films are alternately stacked, said stackedstructure comprising: films having a same refractive index in respect toa first axis (for example, an X axis) and films having a differentrefractive index in respect to a second axis.
 9. The dual liquid crystaldisplay device according to claim 1, said dual brightness enhancementfilm has a multi-layered structure in which a plurality of thin filmsformed of two different materials are alternately stacked, saidmulti-layered structure comprising: poly-ethylene naphthalate layerswith substantially high birefringence and poly-methyl methacrylate(PMMA) layers with an isotropic structure.
 10. A dual liquid crystaldisplay device capable of displaying images on opposite sides thereof,said dual liquid crystal display device comprising: a transmissiveliquid crystal display panel displaying an image on a display surfacethereof; a reflective liquid crystal display panel formed on the samesubstrate as the transmissive liquid crystal display panel to display animage on a display surface thereof; a light guide disposed under thetransmissive and reflective liquid crystal display panels, said lightguide including: a first light guide block corresponding to thetransmissive liquid crystal display panel and having dot patterns formedon a first surface thereof; and a second light guide block correspondingto the reflective liquid crystal display panel and having V-groovesformed on a first surface thereof; a light source disposed adjacent tosaid first light guide block; a housing in which the transmissive andreflective liquid crystal display panels, the light source and the lightguide are seated, said housing having an opening corresponding to saiddisplay surface of the reflective liquid crystal display panel; a dualbrightness enhancement film provided in said opening of said housing;and a first polarizing plate formed on an outer surface of the dualbrightness enhancement film, an inner surface of the dual brightnessenhancement film facing the second light guide block.
 11. The dualliquid crystal display device according to claim 10, said dualbrightness enhancement film has a stacked structure in which a pluralityof films are alternately stacked, said stacked structure comprising:films having a same refractive index in respect to a first axis (forexample, an X axis) and films having a different refractive index inrespect to a second axis.
 12. The dual liquid crystal display deviceaccording to claim 10, said dual brightness enhancement film has amulti-layered structure in which a plurality of thin films formed of twodifferent materials are alternately stacked, said multi-layeredstructure comprising: poly-ethylene naphthalate layers withsubstantially high birefringence and poly-methyl methacrylate (PMMA)layers with an isotropic structure.
 13. The dual liquid crystal displaydevice according to claim 10, said transmissive liquid crystal displaypanel comprising: a thin film transistor array and a transparentelectrode formed on said first substrate; a second substrate having acommon electrode and a color filter pattern formed thereon; and a liquidcrystal layer disposed between said substrates.
 14. The dual liquidcrystal display device according to claim 13, further comprising: asecond polarizing plate, formed on said first substrate; and a thirdpolarizing plate, formed on said second substrate, through which thelight is transmitted to said transmissive liquid crystal display panel.15. The dual liquid crystal display device according to claim 10, saidreflective liquid crystal display panel comprising: a thin filmtransistor array and a reflective electrode formed on said firstsubstrate; a second substrate having a common electrode and a colorfilter pattern formed thereon; and a liquid crystal layer disposedbetween said substrates.
 16. The dual liquid crystal display deviceaccording to claim 15, further comprising: a second polarizing plateformed on said first substrate; and a third polarizing plate, formed onsaid second substrate, through which the light is transmitted to saidreflective liquid crystal display panel.
 17. The dual liquid crystaldisplay device according to claim 1, the first polarizing plate beingformed on an outer surface of the dual brightness enhancement film, aninner surface of the dual brightness enhancement film facing the secondlight guide block.